what type of quail? what are your temperatures in brooder? have you seen them eat and drink? Any chickens around or used the same incubator or brooder? sorry more questions that answers for now. but with this info we have a better idea of what's going on. good luck.

Japanese quail, im using an electric hen specifically a brinsea eco50, ove seen them eat and drink, i do have chickens but im quite careful to wash hands etc. They havent ever use the same equipment. Every hatch i find i loose a handful to this mystery. A previously healthy chick will just turn up dead, or ill find it doing the above. It would be nice to work out why this happens. I just lost the quail i was trying to help, it was a texas a&m white quail. Its a shame. Thankyou for your help

As hard as it is to figure out it could be as simple as poor genetics. Mom or dad might have some gene that is bad. I know most people who hatch loose a few each hatch so I wouldn't be too over concerned it sounds like its pretty normal. Now if you loose the whole flock then its something really bad. If you are sure the temps are okay and they have proper food and water that's about all you can do. Good luck.